We wish to gain further insight into the molecular events leading to ionizing radiation-induced cell death, and the molecular basis of the oxygen effect; more specifically the roles of DNA single- and double-strand breaks and base damage, and their enzymic repair in these processes in bacterial and mammalian cells. We will also study the role of error-prone repair in the process of X-ray-induced mutagenesis. These studies will be conducted on X-ray sensitive cell lines that we are currently isolating.